Controversial pesticides that may be harmful to bees have been linked to declines in British butterfly populations.

#Neonicotinoids, chemical cousins of nicotine, are already subject to a European Union-wide ban imposed to protect bees.

Now new research suggests they might have had a negative impact on #butterflies across many parts of the UK.

The study, based on data gathered by volunteers at more than 1,000 sites, associated declines in 15 of 17 butterfly species with neonicotinoid use.

Most occurred in England, where crops were most likely to have been treated with the pesticides. Affected species included the small tortoiseshell, small skipper and wall.

In Scotland, where neonicotinoid use had been comparatively low, butterfly numbers were stable.

Ecologist Dr Andre Gilburn, from the University of Stirling, who led the research, said: “Our study not only identifies a worrying link between the use of neonicotinoids and declines in butterflies, but also suggests that the strength of their impact on many species could be huge.”

The pesticides, introduced in the 1990s, are absorbed by wild flowers growing in field margins, many of which provide a nectar source for butterflies and leafy food for their caterpillars.

Scientists have alleged that the chemicals can disrupt the ability of bees to forage and may harm colonies. But the claims, lacking support from field trials, are controversial and not accepted by the UK Government.

A two-year ban on using neonicotinoids on flowering crops was imposed by the EU in 2013. Earlier this year, the Government exercised its right under the ban to allow oilseed rape crops in certain regions to be treated with the pesticides.

Results of the new research appear in the journal PeerJ.

Dr Tom Brereton, Head of Monitoring at Butterfly Conservation, said: “We are extremely concerned with the findings of the study and are calling for urgent research to see whether the correlations we found are caused by neonicotinoid use, or some other aspect of intensive farming.

“Widespread butterflies have declined by 58% on farmland in England over the last 10 years, giving concern for the general health of the countryside and for these and other insects in particular.”

Co-author Professor Dave Goulson, from the University of Sussex, said: “Many of us can remember a time when our meadows and hedgerows had far more butterflies, bees and other insects than today.

“This study adds to the growing mountain of evidence that neonicotinoids are one of the causes of these declines.”